The neural crest are cells that emerge shortly after neural tube closure and give rise to the wide variety of neuronal and non-neuronal derivatives that make a large number of head structures and the peripheral nervous system. These cells go from a non-motile, closely adherent cell type, to a highly motile one that allows them to migrate rapidly throughout the embryo and reach distant areas where they differentiate. In addition, neural crest cells encompass a stem cell- like population that can give rise to neurons, glia, melanocytes, facial bone, cornea, etc. The range of birth defects caused by neural crest cells misdirection or death goes from cleft palate (failure of the neural crest to close both sides of the face) to Hirschprung disease/Megacolon (failure of the neural crest to colonize the colon) to Neurofibromatosis (scattered small tumors of neural crest origin). Little is known about the underlying mechanism directing the process of neural crest migration. My preliminary data showed that Slit axonal chemorepellants are important in timing the entry into the gut of one population of neural crest versus another. The goal of the proposed study is to examine the mechanism by which Slit molecules, possibly through its putative Robo receptor repeal trunk, not vagal neural crest migration. Specifically, this project will: a) Examine the function of Robo receptors in repulsion of trunk neural crest migration in cells, b) Determine the role of Slit in preventing trunk, but not vagal neural crest from entering the gut. In summary, these experiments will contribute to our understanding of the multiple roles that Slit chemorepellants play in the formation of the gut by preventing trunk neural crest migration into its region and if the repulsive effects observed in trunk crest cells are Robo mediated. Narrative The goal of the proposed study is to examine the roles and interactions between Slit and Robo molecules have on vagal and trunk neural crest guidance and migration. Altogether preliminary data suggest that there is more to Slit molecules than being just a chemorepellant molecules, that they may be involved in other functions besides guidance. However, it is still not known why trunk neural crest cells will not enter the forming gut while vagal will. It is the aim of this proposal to investigate further this possibility by looking at Slit function in vagal and trunk crest migration of neural crest cells and in looking for Robo's role in this phenomenon. The significance of these experiments stems from its novel approach to study neural crest migration and the mechanism by which Slit molecules guide them during development. Very important, we still do not understand the mechanisms by which Slits have a dual function in both inhibiting and stimulating motility of trunk, not vagal neural crest cells. I propose to study these questions through a multi-faceted approach: embryological and cell biological/molecular. [unreadable] [unreadable]